This invention relates to high resilience polyurethane foams and more particularly to the use of certain organosilicon polymers in the production of such foams.
Basically such high resilience foams are produced by the reaction of highly primary hydroxyl-capped, high molecular weight polyols with organic isocyanates and water. High resilience polyurethane foams are distinguishable in part from conventional hot cure polyurethane foams by the use of such polyols and the fact that high resilience polyurethane foams require little or no oven curing and thus are often referred to as cold cure foams. Such foams are extremely desirable for cushioning applications because of their excellent physical properties, e.g. very high foam resiliency, low flammability, open-celled structure, low flex fatigue (long life) and high SAC factors (load bearing properties).
Because of the high reactivity of high resilience foam ingredients and their rapid buildup of gel strength, sometimes the foam can be obtained without a cell stabilizer, however such foams typically have very irregular cell structure as particularly evidenced by surface voids and the discovery of a proper agent to help control cell structure has remained a major problem in the art.
Attempts to solve this problem with surfactants generally employed in the stabilization of hot cure polyurethane foam have not proven satisfactory because such surfactants tend to overstabilize, causing extremely tight, shrinkaging foam. Nor is the problem corrected by reducing the concentrations of such surfactants, since at concentrations required to eliminate shrinkage, the cells are no longer stabilized satisfactorily and the foam structure becomes irregular, coarse and contains surface voids.
The use of low viscosity dimethylsilicone oils alone as stabilizers for high resilience foams also has various disadvantages. For example, at low concentrations they create metering and pumping problems in the processing of the foam, while at higher concentrations these oils adversely affect the physical properties of the foam. Solvents for such dimethylsiloxane oils that are nonreactive with the foam ingredients e.g. alkanes, hexamethyldisiloxane, and the like, can adversely affect the foam's physical properties in proportion to their concentration and generally create flammability hazards. Furthermore isocyanate reactive diluents, such as polyether triols and the like which do not significantly change the foam's properties, inasmuch as they react into the system and become part of the foam structure, are not satisfactory solvents for dimethylsilicone oils, since not enough oil can be dissolved to provide foam stabilization at practical solution concentrations. High resilience foams are also adversely affected by dimethylsilicones having more than about 10 dimethylsiloxy units per siloxane. For example only 5 or 10 weight per cent of such species in a dimethyl silicone oil can appreciably degrade the foam's physical properties and even cause foam shrinkage.
Moreover, while particularly unique high resilience polyether urethane foam can be prepared employing certain siloxane-oxyalkylene block copolymers as disclosed in U.S. Pat. application Ser. No. 84,181 filed Oct. 26, 1970 now U.S. Pat. No. 3,741,917, or certain aralkyl modified siloxane polymers as disclosed in U.S. Pat. application Ser. No. 305,713 filed Nov. 13, 1972 now U.S. Pat. No. 3,839,384, said disclosures do not teach the use of the novel organosilicon polymers employed in this invention.